Study On Synthesize And Modification Of BaTiO₃-BiYO₃Ceramics With High Temperature Stability Over Wide Range

Multilayer ceramic capacitors (MLCC) are important fundamental components of electronic information technology. At present, X7R MLCC is one of the most widely used and studied MLCC products, but in the aerospace, automobile and military mobile communications industries, as a result of harsh conditions, requirement of its working temperature limit raised up to150℃. The current researches are focused on investigating and developing high working temperature MLCC materials.In this paper, the structure, the dielectric properties and electrochemical impedance spectra of (1-x)BaTiO3-xBiYO3(BT1-BY,BT1:tetragonal phase c/a=1.0059,x=0～0.1) ceramics mixed directly and indirectly were studied. The studies showed that (1-x) BT1-xBY ceramics mixed directly have bigger crystal cell parameters, higher Curie temperature, higher grain and grain boundary equivalent resistance, and better insulating property. The dielectric peak was depressed and broadened, and all present dispersion characteristics as the increasing of BiYO3content. The phase transition temperature increases firstly then decreases.0.97BT1-0.03BY ceramics mixed directly have low-temperature coefficients of capacitance of high temperature.(1-x)BaTiO3-xBiYO3(BT2-BY,BT2:tetragonal phase c/a=1.0101,x=0.07-0.2)ceramics were made by the normal solid state reactions, the structure and the dielectric properties of (1-x)BT2-xBY were studied, addition of BiYO3can flatten curie peak and exhibit diffused phase transition. The structure and the dielectric properties of0.9BT1-0.1BY and0.9BT2-0.1BY were studied, the results show that0.9BT1-0.1BY have bigger crystal parameter, higher dielectric content but Worse temperature stability.MgO doped BT system can enhance the temperature stability of0.97BT1-0.03BY effectively. This paper focused on structure and properties of MgO doped BaTiO3-BiYO3system. When the doping content of MgO is2.2mol%, the dielectric properties is optimal, meeting the X8R requirements with ε~1617, tanδ~-1.5%at1 kHz,|△C/C|≤±15%(-55-155℃).The BiYO3-BaTiO3ceramics modified with BiYbO3further enhance their properties, which depressed dielectric properties and broadened dielectric peak. The phase transition temperature decreases firstly then increases. The structure, the dielectric properties and relaxor phenomena of (1-x) BaTi03-xBiYo.5Yb0.503(BT-BYYb) ceramics are studied. The studies showed that BiYbO3-modified BaTiO3-BiYO3system exhibited more diffused phase transition and better temperature stability than BT2-BY system. The best performance components were0.89BT2-0.11BYYb and0.88BT2-0.12BYYb, which meet the X8R requirements respectively at1kHz with: ε~1330tanδ~0.0076,△C/C|≤±15%(-55~150℃) and ε~1032, tanδ~0.012,|△C/C|≤±15%(-55~170℃).